That is how long it took President Barack Obama to announce the surprise new ban on Wall Street banks’ trading with their own capital and owning hedge funds. That was back in January 2010. The ensuing three-plus years of industry lobbying, intra-governmental infighting and regulatory uncertainty took the “devil-is-in-the-details” cliché’ to a new level.

On Tuesday, we should see the fruit of those labors, afinal version of the rule named after the former Federal Reserve chairman Paul Volcker that should come into effect in 2015.

One paradox stands out: The Wall Street that will receive the Volcker rule is profoundly different from the one the Obama administration targeted at its outset.

In grammatical terms, Tuesday’s publication of the new rule is more of a period than a new paragraph, an endpoint rather than a harbinger.

In the 1,419 days between the president’s announcement and Tuesday’s publication, the global financial industry has changed dramatically, mostly in the direction the Volcker rule sought to push it.

As regulators took their time to figure out Volcker, two key elements of how Wall Street does business changed: the makeup of its trading units and its personnel policies.

On trading, “pure” proprietary trading units—the walled-off teams that played with a bank’s capital—are long gone. Their traders knew Volcker was coming so they took their talents to private-equity firms and hedge funds not covered by the rule.

The remaining businesses also are changing, particularly in the profit engine known as “Ficc”—fixed income, currencies and commodities. As capital regulations penalize riskier activities such as long-dated derivatives, and unpredictable currency and bond markets advise against taking big bets, the likes of Goldman Sachs Group Inc., Morgan Stanley and Deutsche Bank AG are retooling.

“Goldman’s management team is in the process of significantly re-engineering trading by optimizing the balance sheet, triaging underperforming activities, and cutting costs,” Brad Hintz, an analyst at Bernstein Research, wrote to clients last week. Also last week, Deutsche Banksaid it would exitmost of its commodities businesses because of the high costs of regulation.

These moves, and the added restrictions imposed by Volcker, are likely to lead to a reduction in the peaks and (hopefully) troughs in Ficc’s profitability. Those units should become more predictable businesses that are less profitable in the good years but also less prone to blowing up a-la 2008. In that environment, firms controlling the biggest flows of business are likely to win out.

Change is more apparent on the “softer” side of the Street. After a long period in which traders ruled, the balance of power is switching.

“The regulators have been much, much tougher and have come down the hardest on the trading businesses,” says Philip Purcell, who headed Morgan Stanley between 1997 and 2005. “This is going to change the dynamics of a lot of things. The guys with the power at the banks are going to be different people.”

That changing of the guard is already in motion. Morgan Stanley itself transitioned from the trader John Mack to the former McKinsey consultant James Gorman in 2010. More recently, Citigroup Inc., Barclays PLC. and Deutsche Bank all named non-traders to their top echelons. Bank of America Corp., J.P. Morgan Chase & Co. and UBS AG also are run by executives who don’t hail from trading floors.

But the waters are stirring below the C-suite. Take Robert Jain, one of Credit Suisse AG’s rising stars. Mr. Jain had a typical pre-Volcker trajectory: head of global proprietary trading, followed by co-head of global securities in the investment bank. Then, in 2012, he made a switch that few would have contemplated before the crisis—he moved to the asset-management unit, which he now heads.

The reason? “I started at Credit Suisse when I was 26 and I was managing a big portfolio of capital by the time I was 28. Now if I want to manage a big portfolio of capital, I do it for clients,” Mr. Jain, 43, told me.

The Volcker rule will certainly usher in change on Wall Street. As William Silber, a New York University professor and author of “Volcker: The Triumph of Persistence,” a biography of Mr. Volcker, says: “If a firm like Goldman Sachs, which is now a bank, can’t speculate, then the pendulum will swing.”

But a close look at the inner workings of the securities industry suggests that the pendulum has been in motion for some time.

Francesco Guerrera is The Wall Street Journal’s financial editor. Write to him at: currentaccount@wsj.com and follow him on Twitter: @guerreraf72.